Interventional procedures which provide access to body cavities have varied applications for various medical indications. For example, ureteroscopy is often performed using a ureteral access sheath. The small diameter of ureters presents a challenge when attempting to insert an access sheath that is small enough to insert without damaging the ureter and large enough to pass surgical instruments or other objects through to and from the bladder. Other examples of applications which require access to body cavities include intubations, percutaneous procedures, vascular procedures, procedures for the gastrointestinal tract, reproductive tract, lymphatic system or others.
An access pathway may be created through a natural channel in the body, or may be artificially created, depending on the procedure or indication.
Frequently, an access system cannot be easily introduced through a urinary system or other vessels, due to tortuosity in the vessel, strictures within the vessel, or other causes. More particularly, systems which have diameters sufficient to treat the vessel or organ may be too large to pass through problematic areas within the body or body lumen. Systems which can be introduced in a contracted state, and later expanded when within the body, have been developed.
A commonly known technique for enlarging an initial access puncture involves successively introducing larger diameter rods through the access hole and into the internal organ. Systems designed to minimize trauma associated with such techniques include the use of an outer sheath which is radially expandable through various methods. An example of such a system is disclosed in U.S. Pat. No. 5,183,464 to Dubrul et al, entitled “Radially Expandable Dilator.” The dilation tube, or access sheath, is radially expandable from a small diameter to a larger diameter by axial insertion of an expansion member through the axial lumen of the dilation tube.
This system is useful for expanding a puncture site and does not require a contraction to retract the dilator from the body. A catheter for insertion into vasculature is disclosed in U.S. Pat. No. 5,944,691 to Querns et al. This catheter is designed with stripes of rigid material and stripes of expandable material, wherein an expanding member inserted through the catheter causes the catheter to irreversibly expand in the radial direction.
An example of an expandable medical access sheath is disclosed in US Patent Publication 2008/0200943. An elongate tubular member is made of expandable material which can be folded when in its contracted state. The sheath is then expanded by introduction of a dilator through the lumen of the sheath. The material has a first configuration which is collapsed, and a second configuration which is enlarged and which includes elements or structures within the sheath which resist re-collapse. However, pressure within the vessel may cause the sheath to collapse due to the generally flexible nature of the material.
It would therefore be beneficial to have a system and method for accessing a vessel in the body which has a variable diameter, which can be contracted for removal from the vessel, and which will maintain rigidity when open in the vessel.